In a communication system a terminal is used for providing a user interface for the user of the communication system. In other words, by means of the terminal the user may access and communicate over the communication system.
An example of the terminal is a mobile station that may be used in a radio communication system. The mobile station is typically a portable hand-held device that provides, in cooperation with the radio communication system, mobility for the user. When the mobile station is not in use, it is usually positioned in the user's pocket or in a special case or similar. The mobile station typically comprises a keypad for controlling the operation thereof, such as for dialing in a desired telephone number and for controlling various functions of the mobile station. A mobile station is also typically provided with a display. The display may be used for showing various information to the user of the mobile station. Instead of being an entirely hand-held unit, a mobile station may also comprise separate units, such as a base transceiver unit and a separate handset portion and/or a separate headset portion.
Another example is a user terminal for a fixed line communication system. Similarly to the mobile station, the fixed line user terminal, such as a conventional telephone apparatus, typically comprises keys or buttons for the control operations. In addition, a fixed line terminal typically comprises a “hook” that senses whether a separate handset portion and/or a headset portion is placed on the hook indicating that the terminal is not in use. Handheld fixed line terminals that are in the form of a single unit are also known.
The user typically controls the operation and/or functions of the terminal by pressing appropriate buttons on a keyboard of the terminal or by lifting the handset off-hook/placing the handset on-hook or opening/closing a specific cover connected to a switch and so on. Voice activated control systems are also known. For example, when the user wishes to establish a call, he usually selects or fetches the desired destination number by pressing appropriate keys on the keyboard or he may use possible voice activation functions of the terminal. When the user receives a call, the call is typically answered by lifting the handset off-hook, or by pressing at least one key of the keyboard or by opening the special cover of the keyboard. Similarly, any other functions of the terminal may be controlled by pressing appropriate keys or moving one or several components of the terminal to operate an associated switch. The functions and/or operations that need to be controlled may be functions such as switching the terminal between different modes of operation, controlling a keyboard lock or display of the terminal, switching on/off the lightning of the keyboard or the display, or controlling any other special features of the terminal or services provided for the user of the terminal (such as voice mail, short text messages, calendar or alarm functions and so on).
As mentioned above, a mobile station may be provided with a keyboard lock. The basic idea of the keypad or keyboard lock is to prevent the user to mistakenly press any of the keys when this is not desired (e.g. when the mobile station is in the pocket of the user). For example, by means of the lock it is possible to prevent an accidental call establishment to a telephone number that is not actually selected. The keyboard lock may be controlled in alternative ways. According to one possibility predefined keys of the keypad can be used for locking and unlocking the keypad of the mobile station. According to an alternative the closing and opening of a special keypad cover will lock and unlock the keys accordingly.
Whenever the user wishes to control a function of the terminal, he needs to perform a predefined act. For example, when answering a call terminating at a mobile station, it is typically required that the user presses a predefined button or opens a cover of the keyboard or even both. The users may, however, feel the use of the present control arrangements uncomfortable/time consuming. They may also forget to use functions such as the keyboard lock. There are also occasions where automatic control between different modes of operation of the terminal might be desired.
It has been proposed that the terminal is provided with means for detecting a contact between the user's skin and the surface of the mobile station. A prior art proposal is based on use of galvanic skin response (GSR) method. Although these methods have provided e.g. an automated answer to an incoming call, the inventors have found that these contact detection methods may in some instances result in incorrect and/or unwanted operation of the terminal. For example, sensing arrangement based on the galvanic skin response (GSR) may give an output signal when there is some other conductive material than the human skin in touch with the sensing electrodes of the arrangement. The conductive material could be water, dust, a conductive textile, a conductive surface (such as the surface of a table) and so on. Therefore there may be, in some circumstances, a possibility to get an incorrect output signal from the detector arrangement. Other possible detector arrangement, such as a close proximity (CP) detectors may also give false signals, for example when there is a very thin textile between the electrode and the human skin.